The present invention pertains to valves useful in heavy construction application, and more particularly, to valves that are to be used on tubes disposed in off-the-road or agricultural vehicle tires.
It has been known to employ for a variety of purposes valves having stems formed of molded rubber. Such devices commonly include embedded metal inserts inside of which a valve core is contained or housed. In order to provide background material for a consideration of the present invention, reference may be made to U.S. Pat. No. 2,652,067 in which a valve useful in connection with tubes of automobile tires is disclosed, such valve having the aforenoted molded rubber stem and further including an embedded insert and a valve core within said insert. However, the valve structure disclosed in that patent includes a constriction in its bore in the form of an internal resilient annular shoulder which functions to provide the requisite valve seat, or alternately, a stop for a valve core abutment. In either case, such configuration involves a restriction in the pathway provided by the bore. Therefore, such a construction is totally inappropriate in the case of a valve which is required to pass a liquid flow, in which case a substantially smooth and continuously wide diameter bore is essential.
A valve stem formed of molded rubber that has been known before, and which is adapted for use in connection with heavy duty applications, that is to say, off-the-road applications involving operation on rough terrain such as hills, muddy and rocky locations and the like, is that shown hereinafter in FIG. 1 of the drawing. Such a molded valve includes a commonly used short or stub-valve core, chiefly for the reason that such valve core is easier to make and hence less expensive.
A further feature of the known valve device is that interlocking engagement between the valve insert and the molded rubber body is accomplished by reason of rubber material being forced in the molding operation into a groove at the lower end of the valve insert. This will become apparent as the description of the known device proceeds.
The fundamental difficulty that has been encountered in the use of the known heavy duty valve device results from the fact that in order to increase the weight of the previously noted vehicles utilized in heavy duty work on rough terrain, it is customary to add a clacium chloride-water solution to the tire tubes in addition to the requisite amount of air. Of course, it will be appreciated that the calcium chloride is employed in order to prevent the water from freezing under adverse conditions.
It has been discovered that with the current design, that is to say, with the currently used heavy duty valves, liquid splashes onto exposed portions of the valve insert, causing the end of the insert to corrode and thereby allowing the vulcanized bond between the rubber and the metal insert to be broken with consequent loss of air from the tube, and resultant damage to the tire.
Accordingly, it is a primary object of the present invention to overcome the aforesaid problem relating to corrosion of a valve insert in a heavy duty valve environment in which a liquid present in the tube is the source of the problem.
Another object is precisely to eliminate the problem defined so as to avoid expensive flat tire repairs on vehicles of the type described.
Another object is to overcome the problem without resorting to any techniques or methods which would result in hampering the flow of the required liquid into the tubes with which the valves are used.
Yet another object is to accomplish or effectuate the solution explained above but to do so with a minimum of expense involved in providing rubber at the interior of the valve bore.
A still further object is to accomplish the aforenoted solution so as to eliminate the corrosion problem and yet to maintain the interlocking engagement between the bonded rubber and the valve insert.
The above-noted objects, as well as others, are fulfilled by a primary feature of the invention according to which the lower end of the molded rubber valve is formed so as to have a hook-like annular projection at its end and the rubber is molded around this hook-like portion whereby the necessary locking or interengaging relationship is established in a bonded fashion between the metal of the insert and the rubber. Moreover, the rubber is molded at the interior portion in such a way as to define the bore so that the diameter of the bore at its exit end is at least as great as the diameter for the bore defined throughout the metal insert. In other words, the molded rubber at the interior does not act in any constricting way to impede the flow of liquid through the bore, and as aforenoted, the diameter of the bore defined by the rubber is no less than the diameter which prevails throughout the major extent of the interior of the metal insert, that is, the inner periphery or bore as defined by the metal insert.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.